Conduit liner



C, R. MARTIN coNDUIT LINER Filed July 8,' 1933 r Il v..

Patented Dec. 9, 1941 Nnarran stares-cargar iortica 2,265,950 ooNDurr LINER Charles R. Martin, Wauwatosa, Wis., assignor to Allis-Chalmers Manufacturing Company, Mil- Waukee, Wis., a corporation of Delaware Application July 8, 1939,V Serial N0. 283,466

4 Claims.l k(31. k61--17) This invention relates to improvements in liners for conduits conveying a high velocity fluid and particularly to conduits, such as hydraulic turbine draft tubes, which are subject to violent disturbances throughout portions of their length.

When a high velocity fluid flows through a conduit, any bend or irregularity in the conduit is likely to cause disturbance of flow resulting in variations of pressure across the area of the conduit. The turbulence resulting from such flow and pressure disturbances is one of the causes for the phenomenon, known as cavitation which may be dened as a combined corrosive and errosive process. Such cavitation causes a roughening of the conduit walls which increases the cavitational effects and which produces rapid weakening or eventual rupture of the conduit walls. The effect of cavitation is particularly apparent in draft tubes of hydraulic turbines in which an extremely turbulent condition exists below and adjacent the runner. As a consequence of the excessive cavitation taking place, draft tubes have heretofore been plated or lined with metal to provide a smoother surface which is also more resistive to cavitation, than was possible by the use of concrete. Such metal plate liners were heretofore constructed as integral parts of the draft tubes and were immovably fixed in the concrete mass forming the major portion of the draft tube. It was yaccordingly necessary to weldy patches on or insert patches in such plate liners whenever a particularly bad spot was produced thereon for any reason. Such patches are, however, difficult to apply, have the result of decreasing the cross sectional area available to flow and magnify the turbulence which increases cavitation and also further decreases the flow through the lined section of the tube. The present invention provides a liner for high velocity conduits in which a supporting framework is originally mounted in the draft tube concrete when the draft tube is being constructed or is properly anchored in the concrete when used as replacement in an old draft tube and divides the interior surface of the lined draft tube portion into sections. Plates are then secured in an adjacent relation on the frame and are attached to each other along their edges by any suitable means such as welding. A continuous liner is thus formed but the several sections thereof may be readily removed and replaced Whenever cavitation makes such action desirable. Repair of such a liner retains the original ow area of the draft tube and has the effect of inthe conduit or made self-supporting and plates removably mounted on the frame to'provide the lining surface.

Another object'of the invention is to provide a liner for conduits conveying high velocity fluids in which replacement of a portion of the lining will 'only restore'the conduit to its original'inter-` nal area and profile.

Objects and advantages other than those vabove lset forth will Vbe apparent from the following description when read in connection with the accompanying drawing which illustrates a conduit liner of the present invention applied to that portion of the draft tube of a hydraulic turbine which is subject to cavitation and which illustrates such liner partially in section and partially inelevation to show the internal application of the liner to the draft tube and Witha portion of the conduit itself cut away to illustrate the constructionV of the frame and the manner of mounting the plates thereon.

Referring more particularly to the drawing by characters of reference, reference numeral I5 designates a hydraulic turbine runner, shown as being of the Francis type, to which water at high velocity may be supplied by the usual spiral casing (not shown). The flow of water to the runner is controlled by the usual gate-guide vanes 'I mounted in the usual speed ring of which only the lower portion 8 is shown. 'I'he turbine discharges into a conduit or draft tube generally indicated at 9. The draft tube 9 is formed in the massive concrete forming the substructure of the power house and the portion of the' concrete forming the tube adjacent and below the runner 6 is formed with a recess I I therein preferably bounded at its upper and lower peripheral edges I2 and I3 by suitable angular or other metal members I6 and II respectively which extend circumferentially around the edge of the recess and are preferably flush with the inner surface of the draft tube.

The liner itself is formed by a metallic framework and metallic covering plates and is so set into the recess II as to be, in its completed form, in effect a continuation of the inner surfaces of the draft tube. The frame is formed by a plurality of bars I8 extending longitudinally of the axis of the draft tube and connected at their upper and lower ends with the angle rings I6 and I1. Angle brackets I9 are secured to the longitudinal bars I8 in such a position as to receive bars 2| in a horizontal position. The bars I8 are simply straight bars of rectangular section while the bars 2 I, though also rectangular in section, are shaped as segments of an annulus to flt between each pair of longitudinal bars. The bars 2'I may be welded on the brackets I9 or may be bolted thereon as shown, either method of fastening being suitable and hence within the choice of the constructor. 'I'he two sets of bars thus form a frame set into the recess and divide theV recess into a plurality of sections. One of the pairs of bars bounding each of the sections, and

preferably the longitudinal bars I8, are provided with angle brackets 22 to which are secured plates 23. The plates are shaped to conform with the shape of the frame sections both as to outline and as to curvature and thus lie in contact with both pairs of bars around the entire periphery of such section. The angle brackets 22 are provided with spaced holes over which are mounted nuts 26 to receive bolts 21 extending through matching holes in the plate 23 and which bolts are preferably countersunk into such plates. The plates are set into place, the bolts are pushed through the holes in the plates and their brackets 22 and are threaded into nuts 26 whereupon the bolt heads are preferablyr welded to the plate. After all of the plates are mounted, the adjoining edges of the several plates are preferably welded to secure a continuous lining. If desired, holes may be drilled through the plates to permit lling each frame section back of each plate with cement grouting to secure additional backing support for each plate. It will thus be understood that the above described structure provides a liner for a conduit conveying a high velocity uid and in which the permanent frame provides a setting for renewable plates. The use of the present liner permits any cavitation effect to be readily repaired without constriction of the conduit area and without providing projecting edges or surfaces which will recommence and magnify the effects of such cavitation.

Although but one embodiment of the present invention has been illustrated and described, it is to be understood that various changes and modiiications may be made therein within the scope of the appended claims without departing from the scope of the present invention.

It is claimed and desired to secure by Letters Patent:

1. In a renewable liner for a conduit conveying a high velocity fluid, a frame mounted in the conduit, and plates mounted on the frame in adjoining relation to enclose the frame, each of the plates being individually mounted and supported on all edges on the frame for removal and replacement from interiorly of the conduit.

2. In a renewable liner for a conduit conveying a -high velocity fluid, a frame mounted in the conduit and having a plurality of longitudinal members and a plurality of circumferential members, and plates mounted on the frame in adjoining relation to enclose the frame, each of the plates being individually mounted and supported on all edges on the frame for removal and replacement frorn interiorly of the conduit, thje edges of said plates being joined to form a-con'- tinuous lining for the conduit.

3. In a renewable liner for a conduit conveying a high velocity fluid, a frame having a plurality of members mounted longitudinally in the conduit and having a plurality of members mounted on the longitudinal members and extending circumferentially of the conduit, said frame mem-f bers dividing the interior conduit surface into sections, and plates conforming in shape to the sections andmounted on and enclosing the frame, each of the plates being individuallyl mounted and supported on all edges on the frame for re' moval and replacement from interiorly of the conduit. v

4. In a renewable liner for a conduit of frustoconical shape for conveying a high velocity fluid,

' a frame mounted in the conduit and forming a'.

CHARLES R. MARTIN. 

